Book Image

PostgreSQL High Availability Cookbook - Second Edition

By : Shaun Thomas
Book Image

PostgreSQL High Availability Cookbook - Second Edition

By: Shaun Thomas

Overview of this book

Databases are nothing without the data they store. In the event of a failure - catastrophic or otherwise - immediate recovery is essential. By carefully combining multiple servers, it’s even possible to hide the fact a failure occurred at all. From hardware selection to software stacks and horizontal scalability, this book will help you build a versatile PostgreSQL cluster that will survive crashes, resist data corruption, and grow smoothly with customer demand. It all begins with hardware selection for the skeleton of an efficient PostgreSQL database cluster. Then it’s on to preventing downtime as well as troubleshooting some real life problems that administrators commonly face. Next, we add database monitoring to the stack, using collectd, Nagios, and Graphite. And no stack is complete without replication using multiple internal and external tools, including the newly released pglogical extension. Pacemaker or Raft consensus tools are the final piece to grant the cluster the ability to heal itself. We even round off by tackling the complex problem of data scalability. This book exploits many new features introduced in PostgreSQL 9.6 to make the database more efficient and adaptive, and most importantly, keep it running.
Table of Contents (18 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Checking the pg_stat_activity view

Another source of valuable troubleshooting information is PostgreSQL itself. There are numerous views, tables, and functions dedicated to tracking and reporting various statistics and operating statuses for each hosted database. Principal among these is the pg_stat_activity view.

This view tells us what every database client is doing, where it is connected from, which user account it is operating under, and other important values. When administering a highly-available database, we must either have iron control over what executes in the database or the ability to quickly and easily assess its execution state. Besides using this data to track suspicious activity, we can also cancel long-running queries or Cartesian Products, or simply examine the connection turnover.

We probably use this view into the database more than any other, and it forms the backbone of several monitoring utilities as well. Let's explore just why this system catalog is so indispensable...